It is known that tooth-form data indicating tooth forms including the shapes of crowns of teeth is used in dental computer-aided design (CAD) and computer-aided manufacturing (CAM) software with various functions. For example, it is known that arrangement information indicating the positional relationship between at least a subject's first molar and second molar is obtained from a captured image of the subject's oral cavity, and, from the obtained arrangement information, the eruption date of another subject's second molar is predicted (for example, see Japanese Laid-open Patent Publication No. 2012-45247). It is also known that the position and direction of an object for recognition are detected, and, by using the object for recognition whose position and direction are detected, the spatial relationship between a dental patient's maxilla and mandible is captured (for example, see Japanese National Publication of International Patent Application No. 2009-501616).
It is known that the coordinates of movement measurement data at the maximal intercuspal position obtained from the masticatory movement locus of a dentition are matched to the coordinates of shape data obtained from a dentition plaster model of the maxilla and the mandible in a basic state by a conversion matrix (for example, see Japanese Laid-open Patent Publication No. 9-238963). It is known that a collision between 3D models is calculated using a boundary volume layer such as an AABB tree and a spatial distribution structure such as a BSP tree, Oct-tree, and kd tree, and an occlusal position where a virtual maxilla and a virtual mandible contact each other is detected (for example, see Japanese National Publication of International Patent Application No. 2013-520251).
However, a jaw image corresponding to scan data obtained by a dental 3D scanner device has a direction and a tilt in accordance with a scan state. The direction and position of the jaw image is modified by a user who uses the jaw image to a desired direction and position. For example, to use a virtual articulator that simulates a human jaw movement in order to create a dental prosthesis, a user may arrange a maxillary image and a mandibular image such that an occlusal surface passing through a portion where maxillary teeth occlude with mandibular teeth matches a certain reference surface. It is burdensome to arrange the maxillary image and the mandibular image on a CAD screen such that the occlusal surface matches the certain reference surface. The process of arranging the maxillary image and the mandibular image such that the occlusal surface matches the certain reference surface may place an excessive burden on the user.
An occlusal image in a state where maxillary teeth occlude with mandibular teeth is obtained by superimposing maxillary and mandibular scan data obtained by separately scanning the maxillary teeth and the mandibular teeth on fitting scan data obtained by scanning the maxillary teeth and the mandibular teeth in an occlusal state. To omit the process of obtaining fitting scan data, various technologies are proposed to generate an occlusal image by combining a maxillary image corresponding to maxillary scan data and a mandibular image corresponding to a mandibular scan data. However, a maxillary image and a mandibular image each have a direction and a tilt in accordance with a scan state. Therefore, it is not easy to adjust the positional relationship between a maxillary image and a mandibular image, each having a direction and a tilt in accordance with a scan state, to be able to generate an occlusal image. In view of the above circumstances, it is desirable to identify the occlusal state of a maxillary image and a mandibular image corresponding respectively to maxillary teeth shape data and mandibular teeth shape data.